The Q347 flow rate is one of the foundations for the specification of minimum residual flows. Q347 can be determined with the aid of measurements or appropriate estimation methods.
In 1992, a recommended method for estimation of the Q347 flow rate in Alpine catchments was published by what was then known as the Swiss National Hydrological and Geological Survey (SNHGS), which also provided a simple software program. However, no methods were available for the Central Plateau, the Jura mountains or the lower-lying areas of southern Switzerland.
In 1996/97, therefore, a new, regionally differentiated estimation method was developed, which is based once again on a statistical approach but applicable to the whole country. As the collection of model input data is an elaborate process, requiring the use of a Geographical Information System, the decision was taken not to develop a PC program that would permit estimation for any desired Swiss catchment area. Instead, the results were to be translated into a cartographic form.
The 1:500,000 map "Elements for determining Q347 flow rate" combines measurements and values obtained by modelling. The latter represent rough estimates, which could be improved with the aid of more elaborate methods. Such values generally need to be verified with the aid of a short series of measurements.
Last modification 15.11.2019